A meta-analysis of physiological stress responses to natural environments: Biophilia and Stress Recovery Theory perspectives

Several theories, including the Biophilia Hypothesis and Stress Recovery Theory, promote the positive effects of connection to nature on human health and well-being. This article builds on these theories by presenting the results of a meta-analysis of experimental studies on the effects of natural environments on physiological stress. Through a systematic review process, 47 articles were included in the analysis, with a combined sample size of 2430 participants. The overall findings of the study indicated that natural environments had a small to medium effect on reducing physiological stress, compared to equivalent exposure to urban environments. This finding broadly supported both Stress Recovery Theory and the Biophilia Hypothesis. However, subgroup analysis indicated that the stress state of participants was not related to the effect of natural environments in reducing human stress, which contradicts one of the foundations of Stress Recovery Theory. Similarly, uncertain results were obtained regarding type of exposure to environments (immersion, laboratory exposure, or virtual reality), the effects of natural environments on participants with health conditions, and sensitivity of particular outcome measures. The meta-analysis provided general evidence for the theoretical landscape, whilst raising questions as to certain aspects of the theory and the experimental body of knowledge available to support them.